1. Field of the Invention
The present invention relates to a novel oxazolidine compound that is used advantageously as a latent curing agent for curable ingredients such as epoxy resins, urethane resins and modified silicon sealant materials (i.e., terminal silyl group-containing resins) and to a curable resin composition containing such curable ingredients and such an oxazolidine compound.
2. Description of the Related Art
Heretofore, it has been known to use oxazolidine compounds as a latent curing agent for one-component curable resin compositions containing curable ingredients such as epoxy resins, urethane resins, and modified silicon sealant materials. This is to utilize the properties of oxazolidine compounds which is that they are readily hydrolyzed in the presence of humidity (moisture) to form secondary amines, which react with an epoxy group of epoxy resins or an isocyanate group of urethane prepolymers or they serve as a catalyst for condensation reaction of hydrolyzable silicon-containing group of hydrolyzable silicon-containing group-containing compounds to cause their curing.
However, oxazolidine compounds when used as a latent curing agent generally exhibit excellent depth curability of the obtained curable resin composition but have the problem that they have poor storage stability.
To cope with this problem, oxazolidine compounds having a bulky group in the vicinity of the nitrogen atom in the oxazolidine ring have been proposed in JP2001-192374 A (the term xe2x80x9cJP XX-XXXXXX Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d). In this publication, it is described that the oxazolidine compounds when used as a latent curing agent impart good storage stability and depth curability to the obtained curable resin composition.
However, the conventionally known oxazolidine compounds including those described in the above-mentioned publication when used as a latent curing agent have the problem that the obtained curable resin compositions have poor storage stability. In particular, they have the problem in that the storage stability is aggravated when the curable resin composition is in a state where it contains only a curable ingredient and a latent curing agent, that is, in a state where other compounding ingredients such as fillers, plasticizers and thixotropic agents are not compounded in it. If the storage stability of when the curable resin composition is in a state where it contains only a curable ingredient and a latent curing agent is low, it causes problems such as a reaction (increase of molecular weight) proceeds during its storage and when the resin composition is mixed with other compounding ingredients to produce a product, the viscosity of the product may increase to aggravate the workability or deteriorate the adhesion of the product to an adherend to decrease its performance such as adhesive properties.
Therefore, an object of the present invention is to provide a curable resin composition that has excellent curability and excellent storage stability, in particular, excellent storage stability in a state where it contains only a curable ingredient and a latent curing agent. Another object of the present invention is to provide a novel oxazolidine compound that is used as a latent curing agent in such a curable resin composition.
The present invention provides an oxazolidine compound (hereinafter, referred to as a xe2x80x9ccompound of the present inventionxe2x80x9d) represented by the following formula (1). 
[R1 represents a hydrocarbon group having 1 to 6 carbon atoms; R2 and R3 independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R2 and R3 combine to form an alicyclic ring or an aromatic ring; R4 and R5 independently represent a methyl group or an ethyl group; R6 represents a single bond or xe2x80x94(R7xe2x80x94NHCOOxe2x80x94R8xe2x80x94OCONH)pxe2x80x94, R7 and R8 independently represent a divalent organic group, and p represents an integer of 1 to 15; m represents 2 or 3; n represents an integer of 1 to 3].
Also, the present invention provides a curable resin composition (hereinafter, referred to as a xe2x80x9ccomposition of the present inventionxe2x80x9d) containing (a) an epoxy group-containing compound, (b) an isocyanate group-containing compound, (c) a hydrolyzable silicon containing-group-containing compound, a mixture of (a) and (b) described above, or a mixture of (a) and (c) described above, and the above-mentioned oxazolidine compound.
The compound of the present invention when used as a latent curing agent for the curable ingredients such as epoxy resins, urethane resins, and modified silicon sealant materials have excellent curability, in particular excellent surface curability and excellent storage stability, in particular, excellent storage stability in a state where the resin composition contains only the curable ingredient(s) and latent curing agent, and thus can be used very effectively.
Also, since it contains the compound of the present invention, the curable resin composition of the present invention has excellent curability, in particular excellent surface curability and storage stability, in particular, excellent storage stability in a state where the resin composition contains only the curable ingredient(s) and latent curing agent, and thus can be used very effectively.